1. Field
One embodiment of the present invention relates to a printed circuit board, and more particularly to a printed circuit board capable of mounting thereon three-terminal regulator ICs of different terminal-pin arrangement patterns.
2. Description of the Related Art
Three-terminal regulator ICs include DIP-type ICs that are mounted on a printed circuit board with their input, output and ground terminal pins inserted in the board, and SMT-type ICs that are mounted on a printed circuit board with their input, output and ground terminal pins connected to pads formed on the board. The invention relates to a mounting structure for SMT-type three-terminal regulator ICs.
Three-terminal regulator ICs of different makers or of different levels of performance have terminal pins arranged in different patterns.
Accordingly, a plurality of pad arrangements must be prepared for printed circuit boards in light of the arrangement patterns of the terminal pins of three-terminal regulator ICs.
However, to design a plurality of types of printed circuit boards that have different pad arrangements, huge cost is required.
In view of the above, a printed circuit board has recently been developed, which can selectively mount thereon three-terminal regulator ICs of different terminal-pin arrangement patterns.
For instance, three pads are arranged on a printed circuit board with a certain pitch along one side of a three-terminal-regulator-IC mounting region defined on the printed circuit board, and three pads are arranged with a certain pitch along the other side of the mounting region.
When a three-terminal regulator IC having a first terminal-arrangement pattern is mounted on the printed circuit board, two of the three pads along the one side are selected, and one of the three pads along the other side is selected. The terminal pins of the regulator IC are connected to the selected three pads.
Further, when a three-terminal regulator IC having a second terminal-arrangement pattern different from the first terminal-arrangement pattern is mounted on the printed circuit board, one of the three pads arranged along the one side is selected, and two of the three pads arranged along the other side are selected. The terminal pins of the regulator IC are connected to the selected three pads. (See, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-283069)
However, the printed circuit board disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-283069 has complex circuitry, since the pads arranged in pairs symmetrically with the three-terminal-regulator-IC mounting region interposed therebetween are connected by respective semiconductor patterns. Furthermore, when a pad corresponding to a certain terminal pin is selected, it is necessary to rotate the three-terminal regulator IC through 180°. Thus, the mounting operation is also complex.